This application claims the priority of German Application No. 199 17 502.0, filed Apr. 17, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method for automatically controlling the temperature of the interior of motor vehicles using an electronically controlled air-conditioning system having an evaporator, devices for adjusting the fresh-air fraction and the recirculating-air fraction in the vehicle interior, as well as devices for sensing an evaporator temperature, an interior temperature and an outside-air temperature.
Methods of this type have been known for some time. With respect to the technical background, reference is made, for example, to the articles xe2x80x9cElectronic Temperature Control xe2x80x94A Method for Improving the Comfort and the Operability of Vehicle Heatersxe2x80x9d (VDI-Berichte No. 515, 1984, Page 161) and xe2x80x9cControl Systems and Automatic Control Systems for Heating and Air-Conditioning Systems in Motor Vehiclesxe2x80x9d (VDI-Berichte No. 515, 1984, Page 167).
In the cooling operation, at outside temperatures of above 25xc2x0 C. and when the outside air humidity is high, air conditioners of this type (in the form of automatic interior temperature control systems) reach the lowest output temperatures using either a recirculating air operation or an increased recirculating-air fraction in comparison to the fresh-air fraction. In the case of known air-conditioners, the recirculating air fraction is therefore increased at temperatures of above 25xc2x0 C. up to 100% when the deviation (Y) of the actual interior temperature from the desired interior temperature exceeds a defined threshold. However, by means of this control quantity Y, the outside air humidity cannot be determined, which nevertheless has a high influence on the control quality. Mainly in coastal regions with average outside temperatures of between 25xc2x0 C. and 30xc2x0 C. and a high outside air humidity, the known method results in a constant swinging back and forth between a recirculating-air operation and a fresh-air operation. This becomes noticeable to the vehicle occupants by rising ventilation outflow temperatures, fluctuating interior temperatures and a stuffy odor whenever the air conditioner switches off the recirculating-air operation or the recirculating-air fraction.
Furthermore, for avoiding the stuffy odor, the so-called reheat or counterheat method is known. In this case, by cooling the air to values barely above the zero point at the evaporator, the air is dried. As a function of the defined interior temperature, the dried and cooled air must then be heated again. This results in considerable expenditures of energy.
It is an object of the invention to eliminate the above-mentioned disadvantages and, particularly at a high outside air humidity, permit a comfortable and energy-conscious control.
This object is achieved by a method for automatically controlling the temperature of the interior of motor vehicles by means of an electronically controlled air-conditioning system having an evaporator, devices for adjusting the fresh-air fraction and the recirculating-air fraction in the vehicle interior, as well as devices for sensing the evaporator temperature, the interior temperature and the outside-air temperature. The recirculating-air fraction is increased: when the recirculating-air fraction is lower than 100%; when the deviation of the actual interior temperature from the desired interior temperature exceeds a defined first threshold, when the outside temperature remains essentially constant; and when the evaporator temperature rises. Advantageous further developments are described herein.
The known systems and methods for automatically controlling the inside temperatures of motor vehicles by means of an electronically controlled air-conditioning system normally already contain an evaporator, devices for adjusting the fresh-air fraction and the recirculating-air fraction in the vehicle interior as well as devices for sensing the evaporator temperature, the interior temperature and the outside-air temperature.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.